The present invention relates to an improved electrical transmission and control system for use in a central vacuum cleaning system having a centrally located A.C. power turbine and one or more remote cleaning units equipped with low voltage agitator motors. A single pair of conductors interconnected between the central system and the remote unit permit the operator to switch on the agitator motor with the A.C. vacuum system, or to switch on the vacuum system only, by introducing through the wire pair a current flow that is sensed by a current sensor that, in turn, controls the power to the A.C. vacuum motor.
My U.S. Pat. No. 3,525,876, describes and claims a similar type of two-wire power transmission and control circuit which supplies low voltage D.C. power to an agitator motor and which uses a low voltage A.C. control circuit. While the circuit of that patent works satisfactorily, many problems, both physical and electrical, arose because major circuit components had to be constructed in the handle of the remote cleaning unit hose.